(1) Field of the Invention
This invention relates generally to DC-to-DC converters and relates more specifically to boost switching regulators having a highly stabilized output.
(2) Description of the Prior Art
A boost converter (step-up converter) is a power converter with an output DC voltage greater than its input DC voltage. It is a class of switching-mode power supply (SMPS) containing and at least one energy storage element. Filters made of capacitors (sometimes in combination with inductors) are normally added to the output of the converter to reduce output voltage ripple.
The key principle that drives the boost converter is the tendency of an inductor to resist changes in current. When being charged it acts as a load and absorbs energy (somewhat like a resistor), when being discharged, it acts as an energy source (somewhat like a battery). The voltage it produces during the discharge phase is related to the rate of change of current, and not to the original charging voltage, thus allowing different input and output voltages.
FIG. 1 prior art shows the basic principle of a Boost converter consisting of two distinct states depending of the state of main switch S:                In the On-state, the main switch S is closed, resulting in an increase in the inductor current;        In the Off-state, the main switch S is open and the only path offered to inductor current is through the fly back diode D, the capacitor C and the load R. This results in transferring the energy accumulated during the On-state into the capacitor.        
Feedback and control circuitry can be deployed with the circuit to regulate the energy transfer and maintain a constant output within normal operating conditions.
From a power management standpoint, one of the critical blocks that hinder the complete integration of switching DC-DC converters is the frequency compensation circuit, whose design is based on the values of off-chip LC filter components. Since these LC filter values vary, because of various design requirements, manufacturer tolerances, and/or parameter drifts, integration of a compensation circuit implies a non-optimal control design and a lower bandwidth solution.
The direct impact of a non-optimal compensation circuit is reflected in the transient response performance of the regulator, which is critical for voltage accuracy and stability in portable applications when driving switching loads. The poor transient response can be offset by increasing the size of the output capacitor, requiring more PCB real estate and cost.
It is a challenge for engineers to design the higher bandwidth control loop without causing instability program.
There are known patents or patent publications dealing boost converters:
U.S. Patent Publication (US 2009/0001943 to Szlezak et al.) discloses a boost converter circuit that includes a power supply, an inductor coupled to the power supply to receive current from the power supply, a diode coupled to receive current from the inductor and coupled to provide current to a load as an output, an inductor switch coupled to a node between the inductor and the diode for selectively switching current from the inductor anyway from the diode, and a ramp circuit. The ramp circuit is coupled to the node between the inductor and the diode, and is configured to selectively sample a voltage at the node between the inductor and the diode via a sampling switch and use the sampled signal to produce a stabilization ramp to stabilize the output.
U.S. patent (U.S. Pat. No. 7,528,590 to Wei) proposes a DC-to-DC boost converter circuit receiving a DC input voltage and converting it to a DC output voltage at a different voltage level than the DC input voltage. The DC-to-DC boost converter includes a switching power converter for receiving the input voltage on an input and converting the input voltage to an output as the DC output voltage in response to pulse control signals. A switching controller generates the pulse control signals during a switching cycle. The switching controller further includes pulse-skipping circuitry for generating a pulse width modulated signal to the switching power converter. A pulse width of the pulse width modulated signal is decreased responsive to a voltage level of an output voltage of the DC to DC boost converter being less than a control saw tooth waveform and the pulses width of the pulse width modulated signal is increased responsive to the voltage level of the output voltage of the DC to DC boost converter being greater than the control saw tooth waveform.
U.S. patent application (U.S. Pat. No. 7,202,694 to Eberlein) proposes circuits and methods to sense the current through a coil of an integrated switching converter, applicable to boost and to buck converters. The present invention uses a “replica biasing” technique to avoid a resistor for current measurement. The current through a pass device is mirrored into a replica, having a scale of n and being much smaller in size, of said pass device. The current through the replica is mirrored to another branch of the circuit and back again to achieve a fast stabilization of the current. The current through the replica is mirrored again to an output branch of the circuit, which conducts exactly a fraction 1/n of the current flowing through the pass device. The self-biasing current loop of the invention adapts quickly to the actual current level through the pass device of the switching converter. Accuracies better than 5% are achieved over a wide range of dynamic range.